Spatial pattern and stand structure in subalpine forests of the northeastern Olympic Mountains, Washington

The spatial pattern in three subalpine forest community types was examined and related to stand structure, development and competitive interactions among overstory and understory stems. A Cartesian coordinate system was used to locate, measure and map all live tree stems in each of two subalpine fir (Abies lasiocarpa) stands in different stages of development, one lodgepole pine (Pinus contorta) stand, and one Pacific silver fir (Abies amabilis)-mountain hemlock (Tsuga mertensiana) stand. Spatial statistics, including nearest neighbor, combined count-distance and association analyses, were used to assess univariate and bivariate point patterns and understory/overstory linkages.; All sampled forest stands exhibited shifts in univariate measures of dispersion, from aggregated understory stems to less-aggregated overstory trees. In addition, shifts in bivariate point patterns describing the interaction between understory stems and overstory trees were described. Spatial attraction between understory and overstory stems was shown to change to a more repulsive behavior in a later stage of forest development.; Competitive relationships vary among forests composed of different species that lie at diverse points along a moisture gradient. Consideration of the life history characteristics of the component species in each community type assists in interpreting the mechanisms shaping forest spatial patterns. In addition, the importance of stage of forest development is shown to influence the interactions in each forest, and hence to affect the resultant spatial pattern.